Crystalline layered mixed metal hydroxides (LMMHs) of the monolayer variety have been made in aqueous systems, employing water-soluble reactants (esp. MgCl.sub.2 and AlCl.sub.3), such as in EPO 0.207.811 and U.S Pat. No. 4,790,954. Mixed metal hydroxides of the 2-layer and 3-layer variety have also been made in water systems, such as in, e.g., U.S. Pat. No. 4,812,245. Some of the layered mixed metal hydroxides that have been prepared in aqueous media have been ion-exchanged with ionizable organic compounds to provide organic anions in the compounds, such as in U.S. Pat. No. 4,727,167.
We have now found, unexpectedly, that significantly different properties are advantageously found in crystalline layered mixed metal hydroxides (LMMHs) that have been prepared using non-aqueous material as the reaction media in creating the LMMHs, thus obtaining LMMHs which are substantially anhydrous. This lack of water permits the LMMHs to be used n applications in which the presence of water is detrimental, such as in electrorheological fluids which may be employed under conditions which exceed the boiling point of water; or as additives to polymers; or as additives in oil-based paints or coatings where the presence of more than a very minor amount of water is detrimental.